Carrera Injectors - When do you replace?

[movin]

How long will the injectors last? And what is a typical symptom of worn injectors?

[PCA7GGR]

Using the right fuel, injectors can last the life of an engine, Instead of replacing them, have then "bench" flowed. The test will determine the current flow rate and spray patter. Most times, the shop can also correct the flow rate and spray pattern to factory specs.

I am planning to convert my twin plugged, crank fired 2.8 from 40 IDA Webers (too small) to a Haltec controlled injection system using a set of used 3.2 injectors. It ran me less than $200 to have the six used injectors tested and corrcted.

Hope this helps.

[BGCarrera32]

When I purchased my Carrera, it had pretty high but unknown miles on the engine. I had 1 bad injector which I replaced, as it was fouling the plug in that cylinder.

A year after I replaced that injector, I pulled the engine to do a variety of maintenace tasks. Upon removing the intakes, the back of each valve was visible. The valve who's injector had been replaced was bright and clean, you could see the bronze color of the valve guide seat poking through the cylinder head. The other 5 valves varied, from slightly cruddy to larger hard carbon/crust deposits. Moral of the story, the other 5 injectors were no longer performing at optimum metering. The pintle valve in the injector was no longer able to meter appropriatley.

As far as I know, if you have a Bosch injector (like the ones used with Motronic on our Carrera) bench flowed, other than cleaning I'm not sure the *average* shop can service those. (I may be wrong on this but I wouldn't trust them).

[CarreraS2]

I don't know how much Carrera injectors are, but would guess they are expensive.

I wonder if there is a compatible injector used on a different car. On "big 6" engined BMWs from the '80s, for example, someone figured out that Bosch injectors used on certain years of the Ford Mustang work perfectly! Same part, different number. And, of course, a fraction of the cost.

For the BMWs, the Ford injectors are cheap enough to warrant simply replacing them as a maintenance item after they have done a lot of miles.

[PCA7GGR]

When you have injectors "bench" flowed, they are then cleaned to bring them back to factory spec.

[old_skul]

Carrera injectors from Pelican are 70.25, and the seals (which you need) are 4.75.

[movin]

So a symptom may be, running on the rich side and oil dilution?

[BGCarrera32]

Seals come with new Bosch injectors for the Carrera, no need to order seperately.

A run ruch condition is possible if the pintle valve in the injector no longer closes properly or the solenoid has somehow weakened. Another possibilty (this happened on my car) although not very common is a fuel pressure regulator that has expired, however my guess is that typically when that happens it causes a lean-out condition creating hard starts.

[stlrj]

I found that the new style injectors that use a director plate instead of a pintel work very well.

The ones I'm using are called Multec injectors from a Chevy 3100 engine at a fraction of the cost of stock injectors. As it turns out, the 996's use the same type injectors too.

996 injector



Multec injector


Cheers,


Joe Garcia
86 Carrera
Redwood PCA since 1976 ( former tech chair)

[movin]

Joe,
Just read a tec. comparison between Bosch and Multec and you're right! The Multec's are an improvement over the Bosch! Are you using those Multec injectors in your '86? How's it running? Is it a no mod. installation? Would they fit my '87? Lastly, does Pelican sell these?
BTW, the Vette guys say the Ford Mustang injectors are better in their application than the OEM and cost much less. Seems everyone is into swapping parts and experimenting.

[stlrj]

I've gone back and forth on the stock injectors and the Multecs, as far as I can tell, are superior, better throttle response, smoother crisper accelleration, better idle.

The only downside is it needs some tuning to make them work on the Carrera engine. I installed a start relay to give it a bit more fuel so it would start when warm and adjusted the AFM to compensate for the lower flow rate of the Mulltec.

Considering the mods to make it work, I am very pleased with the results and would never go back to the stock injectors, there is such a vast improvement in low end torque with the Multecs that it makes chipping unnecessary.

For the money, I don't think you will find a more cost effective, invisible and technically elegant performance mod.

Cheers,

Joe Garcia
86 Carrera
Redwood PCA since 1976

[stlrj]

Here's what it looks like on my engine:



Joe

[movin]

Was the impedence a good match to the DME(comparable to the Bosch)?
Further reading on various searches revealed some reliability problems with the Multec's, shorted coils and intolerance to fuel system cleaners. Some other sites actually go on to say the pintle style is still better! One site mentioned a Bosch DRI injector that elliminates the accumulation problem at the tip.

[stlrj]

The impedence on the Multec injector is 12.5 ohms. If I recall, the Bosch injectors were about the same. GM specifically warns against using fuel injector cleaners on Multecs to prevent shorted coils and since they are deposit resistant, cleaners are not necessary.

[ssetek]

most injectors come in 2 flavors peak and hold and saturated,

p&h low resiatance 2-3 ohms must run a inline resistor box
saturated high resistance 12 ohms drop in

[Craig Roche]

So, being that I'm a rookie! Can a guy just plug them in and go?

[ChrisBennet]

This company's web site details some problems with the Multecs. Linder Technical Services, Home of the Injector Guru
Their "fix" for the Multecs is replacing them with Bosch injectors.
I wonder if the "problem Mutecs" are a different generation or model.
-Chris

[raceman]

so let's see.The Multecs offer better throttle response,smoother idle and crisper acceleration.ln order to benefit from all this one must adjust the AFM? and install a start relay? l`m not sure what you mean here,could you elaborate on both procedures? l`m planning on doing injector sevice on my 84,cleaning/balancing the stockers or replacement.The stockers are pretty much maxed out,which is how most factory systems are designed.Talking to the guys at RC engineering it appears there is no incremential upgrade in a bosche part so the Multec might be an option

[fastpat]

Originally posted by stlrj
I found that the new style injectors that use a director plate instead of a pintel work very well.

The ones I'm using are called Multec injectors from a Chevy 3100 engine at a fraction of the cost of stock injectors. As it turns out, the 996's use the same type injectors too.

996 injector



Cheers,


Joe Garcia
86 Carrera
Redwood PCA since 1976 ( former tech chair)

Those are the Design III disc type injectors. A good upgrade, I'm investigating it now. But if someone else knows the answer, please post it.

[chuckr]

I had the injectors on my 89 911 rebuilt and flow matched
by EBS. Check their website for info and prices. They provide
a chart on before and after. My injectors had about 122,000
miles on them